The northbound shoulder on Highway 49 just north of Lime Kiln Road will be closed until noon as Caltrans workers clean up 20 to 30 gallons of spilled diesel fuel, according to the California Highway Patrol.

A big rig with a busted fuel tank spilled the gas at about 7:14 a.m., according to the CHP’s traffic incident Web site.

No lanes have been blocked, the CHP reported.

Caltrans and the environmental health department were notified, and cleanup was projected to last until noon, according to the CHP.